Study of the formation of the Arctic cell associated with the two-wave middle-high latitude circulation

Abstract

The formation of the Arctic cell associated with the two-wave middle-high latitude circulation, which is a major atmospheric circulation common to the three-cell and four-cell mean meridional circulations in the Northern Hemisphere, is analyzed using a long period of reanalysis data. In the context of the two-wave middle-high latitude circulation, when the high near the Arctic region from 120°E to 80°W (AH120E80W) weakens and withdraws eastward and the low near the Arctic region from 80°W to 120°E (AL80W120E) strengthens and expands northeastward, the Arctic tends to be controlled by obvious low pressure and associated upward motion, leading to the formation of the Arctic cell. The eastward withdrawal of the AH120E80W is attributed to an eastward retreat of the North Pacific Low, because it promotes the strong anticyclonic wind shear associated with the maintenance of the AH120E80W to migrate eastward. The eastward retreat of the North Pacific Low is induced by the decrease in the width of the East Asian Trough, which results from the response of the high terrain in Central Asia to the weakening of middle-latitude westerly winds caused by a northward shift of the Azores High. On the other hand, the eastward withdrawal of the AH120E80W results in the decay of the Arctic high, causing the winds near the Arctic to change from easterly to westerly. At the same time, the northward shift of the Azores High promotes the strong Icelandic Low to expand poleward. The combination of the Arctic westerly winds and the poleward expansion of the strong Icelandic Low leads to the northeastward expansion of the AL80W120E.